Wireline Standard Data Processing
ODP logging
contractor: LDEO-BRG
Hole: 825B
Leg: 133
Location: Marion Plateau (tropical SW Pacific)
Latitude: 16° 30.961' S
Longitude: 148° 9.457' E
Logging date: October, 1990
Bottom felt: 951 mbrf (used for depth shift to sea floor)
Total penetration: 466.3 mbsf
Total core recovered: 3 m (3.5 %)
Logging
Runs
Logging string 1: DIT/SDT/NGT
The logging report did not provide any information about use of wireline heave compensator.
Bottom-hole
Assembly/Pipe/Casing
The following bottom-hole assembly depths is as it appears on the logs after depth shift to the sea floor. As such, there might be a discrepancy with the original depths given by the drillers onboard. Possible reasons for depth discrepancies are ship heave and drill string and/or wireline stretch.
DIT/SDT/NGT: Bottom-hole assembly at ~67 mbsf.
Processing
Depth shift: As only one run was recorded, no differential depth shift was required. The original logs have been depth shifted to the sea floor (- 951 m).
Gamma-ray processing: NGT data have been processed to correct for borehole size and type of drilling fluid.
Acoustic
data processing: The array sonic tool was
operated in standard depth-derived borehole compensated mode, including
long-spacing (8-10-10-12') logs. The sonic logs have been processed to
eliminate some of the noise and cycle skipping experienced during the
recording. Using two sets of the four transit time measurements and proper
depth justification, four independent measurements over a -2ft interval
centered on the depth of interest are determined, each based on the difference
between a pair of transmitters and receivers. The program discards any transit
time that is negative or falls outside a range of meaningful values selected by
the processor.
Quality
Control
null value=-999.25. This value generally replace recorded log values or results which are considered invalid.
During the processing, quality control of the data is mainly performed by cross-correlation of all logging data. Logging data at hole 825B are of good quality.
Data recorded through bottom-hole assembly should be used qualitatively only because of the attenuation on the incoming signal.
Hole diameter was recorded by the 3-arm mechanical caliper device (MCD).
Additional information about the logs can be found in the "Explanatory Notes" and Site Chapter, ODP IR volume 133. For further questions about the logs, please contact:
Cristina
Broglia
Phone: 845-365-8343
Fax: 845-365-3182
E-mail: Cristina Broglia